1. Field of the Invention
The present invention relates to a protection device and method for an electronic device, and more particularly, to a protection device and method capable of integrating the over-current protection, over-voltage protection and negative voltage protection functionalities for an electronic device.
2. Description of the Prior Art
In modern society with advanced information, people desire to catch various types of information anytime and anywhere, and various portable electronic devices, such as laptops, personal digital assistants (PDA), mobile phones, smart phones, emerge as the times require. In order to process a large amount of data while remaining a small size, there may be sophisticated and complex circuits with high integration inside the portable electronic devices. The internal circuits can normally operate only when provided with a predetermined direct current (DC) bias voltage. A DC voltage exceeding this predetermined voltage or an erroneously inverse DC voltage may damage the sophisticated circuits and disable the circuits. In addition, since the internal circuit elements have limited loading current capability, the internal circuits may be burnt if an incoming current exceeds the current limit of the circuit elements, which causes that the portable electronic devices may fail to operate properly.
In order to prevent the internal circuits from being damaged by the improper bias voltage or current, a general portable electronic device may be equipped with a protection circuit for protecting the internal circuit elements. The conventional over-voltage or negative voltage protection circuit cannot simultaneously provide over-current protection functions; hence, the portable electronic device should be externally connected to a positive temperature coefficient (PTC) thermistor or recoverable fuse for over-current protection. However, the PTC thermistor and the recoverable fuse have a greater internal resistance, which may generate a high temperature after the protection circuits are switched on and off many times. When the system has a larger load, the current flowing through the PTC thermistor or recoverable fuse may increase and generate a greater voltage drop, which easily generates an evil influence on the system. Thus, there is a need for improvement over the prior art.